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Hot enough for everyone

The heat is on, and as we dash from our air-conditioned vehicles into air-conditioned buildings, one can't help wondering how people coped with extreme summer heat in the pre-technology era.

Were they vulnerable to heat exhaustion and heat stroke? Or were they simply tougher than we are?

If you look back through history, it becomes clear that people have long been wise to various strategies for cool living. They built dwellings of stone or adobe, for instance, that kept out the worst of the summer heat. The ancient Egyptians hung damp mats or placed clay jars of water in their homes to cool the surrounding air. During the glory days of the Roman empire, the nobility had their summer gardens filled with snow transported from the mountains.

Visit an older house in the United States and you're likely to notice the high ceilings, open stairwells and large attics allowing warm air to rise. Homes were often designed with windows and halls that created cross-ventilation. Porches or verandas helped provide shade and a place to sit (or sleep) outdoors in the evening. Plantations and farms frequently had summer kitchens - a separate building where a stove or wood fire could be stoked up for cooking without heating the entire house.

This doesn't mean people somehow were immune to heat exhaustion or heat stroke. After all, there's only so much the human body can tolerate.

Heat-related illness happens when the body's temperature-regulating mechanisms break down under stress or exposure to heat. Children and older adults are the most vulnerable, as are individuals with chronic health conditions such as heart disease. But even healthy young adults can fall prey to heat exhaustion or heat stroke if they overexert themselves in hot weather.

Formal statistics might not have been collected 100 or 500 years ago, but people throughout history have died of heat stroke or succumbed to heat exhaustion. For example, accounts of the Crusades, which lasted from 1047 to 1291, describe how medieval knights, hampered by hot, heavy armor, were often outmatched by Saracen armies better equipped and adapted for fighting in the hot desert conditions of the Middle East. Camp followers, camels and soldiers were felled by the hundreds as Alexander the Great marched his troops across the Gedrosian desert in the year 325.

In this sense, it's unlikely our ancestors were that much tougher than we are. Nor did they have to deal with modern-day factors that have turned up the heat - the heat islands created by urban environments, for instance, or the oven-like temperatures inside a parked car, or the use of prescription medications such as diuretics and beta blockers that inhibit the body's ability to cope with hot weather.

Back in the day, however, when people were routinely exposed to weather extremes, they may simply have been more physically adapted to tolerate it. Some interesting studies carried out over the past few decades have found that when athletes train in hot environments, they can improve their physiological response - in other words, they become acclimated and better able to tolerate exercise in hot conditions.

Researchers also have found that when people are passively exposed to heat, they become somewhat acclimatized, especially in their body's ability to dissipate heat.

Whether air conditioning has turned us into a society of wimps is hard to say. Over the course of history, humanity has certainly been forced to endure extreme weather conditions and there's no doubt that countless people have suffered and died because of it. On the other hand, heat exhaustion and heat stroke have become preventable illnesses that needn't claim the number of lives they have in the past. So why sweat when there's a safe and comfortable alternative?